1. Field of the Invention
The present invention relates to a power semiconductor device and a method for manufacturing the same.
2. Description of the Related Art
An insulated gate bipolar transistor (IGBT) is a transistor in which a gate is manufactured using metal oxide silicon (MOS) and a p-type collector layer is formed on a rear surface thereof to thereby provide bipolarity.
Since a power metal oxide silicon field emission transistor (MOSFET) according to the related art has been developed, MOSFETs have been used in regions requiring fast switching characteristics.
However, due to structural limitations of the MOSFET, a bipolar transistor, a thyristor, gate turn-off thyristors (GTOs), and the like have been used in regions requiring high voltage.
The IGBT having low forward loss and fast switching speed characteristics has been widely applied to fields in which is impossible to implement with an existing thyristor, a bipolar transistor, a metal oxide silicon field emission transistor (MOSFET), or the like.
Describing an operational principle of the IGBT, in the case in which the IGBT element is turned on, an anode thereof may have a voltage higher than that of a cathode applied thereto, and in the case in which a gate electrode a voltage higher than a threshold voltage of the element applied thereto, polarity of a surface of a p-type body region disposed at a lower stage of the gate electrode is reversed to thereby form a n-type channel.
Electron current injected into a drift region through a channel derives an injection of hole current from a high concentration p-type collector layer located in a lower portion of the IGBT element similar to a base current of the bipolar transistor.
Due to a high concentration injection of a few carriers as described above, conductivity modulation in which conductivity is increased in the drift region from tens to hundreds of times occurs.
Unlike the MOSFET, since resistive components in the drift region become significantly smaller due to conductivity modulation, the IGBT may have a significantly high voltage applied thereto.
Current flowing toward the cathode is divided into an electron current flowing through the channel and a hole current flowing through a junction between the p-type body and the n-type drift region.
The IGBT is a pnp structure between the anode and the cathode in the structure of the substrate. Therefore, since a diode is not embodied in the IGBT unlike the MOSFET, separate diodes should be connected in inverse-parallel.
The above-mentioned IGBT has main characteristics such as maintenance of blocking voltage, a decrease in conduction loss and an increase in a switching speed.
As the power semiconductor device has a large capacitance, a size of a chip may be increased in order to generate more current, and as the size of a termination region covering an inverse-voltage region is increased, it becomes difficult to secure reliability.
Users gradually require power semiconductor devices capable of withstanding higher transient states.
Therefore, research into structure or processes for forming power semiconductor devices capable of securing high reliability has been recently undertaken.
Patent Document 1 described in the following related art document relates to a diode of a semiconductor device.
The invention described in Patent Document 1 has a configuration different from that of the present invention and the present invention has an effect different from the invention disclosed in the Patent Document 1 and has a more significant effect than the invention disclosed in Patent document 1.